Background Field
The present disclosure relates generally to generating assistance data for positioning and location based services, and in particular, to generating assistance data that includes vertical access information with probabilities of vertical movement.
Relevant Background
Indoor positioning and location based services typically use Received Signal Strength Indicator (RSSI) and/or Round Trip Time (RTT) measurements from access points to determine a position of a mobile device. Assistance data is used to provide a map of the indoor location as well as known positions of the access points. Location based services use the RSSI and/or RTT measurements from access points, as well as the positions of the access points obtained from the assistance data to estimate a position of the mobile device with respect to the map.
Typically, however, the maps used in indoor location based services are two-dimensional, i.e., each floor of a building is independently mapped. Floor changes are generally detected by, e.g., the increased signal strength from access points on different floors. For example, when a mobile device changes from a first floor to a second floor of a building, the signal strength from access points on the first floor will decrease, while the signal strength of access points on the second floor will increase. Based on changes in the received signals, it may be determined that the mobile device is no longer on the first floor, but is now on the second floor. Relying on measurements from received signals to detect floor changes, however, may produce incorrect results. For example, in some locations in a building, such as areas that are open between floors, e.g., areas with balconies, a mobile device may receive strong signals from access points that are on floors that are different than the floor upon which the mobile device is located. Consequently, the mobile device may incorrectly determine that it has changed floors. Conversely, the mobile device may, in fact, have changed floors, but may still be receiving strong signals from access points on the previous floor, which may cause the mobile device to fail to recognize the floor change.